Repetitive paging from a wireless data base station having a smart antenna system

ABSTRACT

A method, system, and machine-readable medium for transmitting a downlink signal in a substantially non directional manner from a communication station to a first remote communication device on a downlink channel. The communication station includes a smart antenna system having an array of antenna elements. The method includes determining a first downlink smart antenna processing strategy for transmitting in a first non-directional manner, transmitting a first downlink message from the communication station in the first non-directional manner using the first downlink smart antenna processing strategy, and repeating transmitting the first downlink message from the communication station in a second non-directional manner. The repeated transmitting is non-identical repetition to facilitate the interference environment being different in the repetition.

RELATED PATENT APPLICATIONS

This is a division of application Ser. No. 10/222,106, filed Aug. 16,2002, which is a division of application Ser. No. 09/676,885, filed Sep.29, 2000, and claims the benefit of priority of those applications.

This invention is related to the following three concurrently filed U.S.patent applications, each assigned to the assignee of the presentinvention, and each incorporated herein by reference:

-   -   (1) application Ser. No. 09/676,887, issued on Jun. 13, 2006 as        U.S. Pat. No. 7,062,244, entitled “DOWNLINK TRANSMISSION IN A        WIRELESS DATA COMMUNICATION SYSTEM HAVING A BASE STATION WITH A        SMART ANTENNA SYSTEM,” to Youssefmir, et al.    -   (2) application Ser. No. 09/667,460, issued on Sep. 21, 2004 as        U.S. Pat. No. 6,795,409, entitled “COOPERATIVE POLLING IN A        WIRELESS DATA COMMUNICATION SYSTEM HAVING SMART ANTENNA        PROCESSING,” to inventors Trott, et al.    -   (3) application Ser. No. 09/676,888, issued on Jan. 3, 2006 as        U.S. Pat. No. 6,982,968, entitled “NON-DIRECTIONAL TRANSMITTING        FROM A WIRELESS DATA BASE STATION HAVING A SMART ANTENNA        SYSTEM,” to inventors Barratt, et al.

BACKGROUND OF THE INVENTION

The present invention relates to radio communications, and moreparticularly to radio communications methods in a cellular or similarwireless communication system between a base stationtransmitter/receiver (transceiver) and a plurality of remote userterminals, in particular for radio communication in a changingenvironment.

In such communication systems it is desirable to use directional antennasystems such as smart antenna systems to increase the signal-to-noiseratio of the communications link and reduce interference. The use ofsmart antenna systems can also provide resistance to multipath andfading.

A smart antenna system includes an array of antenna elements and amechanism to determine the smart antenna processing strategy to increasethe signal-to-noise ratio and/or reduce interference. A smart antennasystem may be a “switched beam” system that includes a beamformerforming several fixed beams and a mechanism for combining one or more ofthe beams. A smart antenna system may alternately be an adaptive antennaarray system that includes a smart antenna processing strategydetermining mechanism that can achieve an infinitely variable antennaradiation pattern that can be adapted according to the processingstrategy for the particular receiving or transmitting situation.

Smart antenna systems may be used for communication on the uplink (froma user terminal to a base station) or on the downlink (from a basestation to a user terminal) or on both phases of communication.

Smart antenna systems may also permit spatial division multiple access(“SDMA”). With SDMA, more than one user terminal of a base station maycommunicate with the base station on the same “conventional” channel,that is, the same frequency and time channel (for an FDMA and TDMAsystem) or code channel (for a CDMA system), so long as the co-channeluser terminals are spatially separated. In such a case, the smartantenna system provides for more than one “spatial channel” within thesame conventional channel.

The transmission RF and interference environments can be relativelyrapidly changing in a cellular system. In a packetized system, theseenvironments may significantly change between sequential packettransmissions. Consider, for example, a cellular system that includes abase station that has a smart antenna system and one or more remote userterminals. In a rapidly changing environment, the determining of theappropriate smart antenna processing strategy needs to be adaptive to anuplink signal received from the mobile user during a time intervalclosely corresponding to the transmission period. Such adaptiontypically uses a radio signal from the user terminal to the basestation, with the smart antenna processing strategy determined usingsuch a received signal.

There is a need in the art for adapting to a rapidly changing RF andinterference environment.

Polling

Consider a cellular system that includes several base stations, eachhaving a set of one or more user terminals. It is known in the art howto determine the smart antenna processing strategy for a smart antennasystem of a particular base station to achieve interference mitigationfrom co-channel user terminals that may be transmitting signals in thesame channel but to other base stations. Such interference mitigationmay be achieved by receiving radio signals at the particular basestation from the interfering co-channel user terminals anddistinguishing the desired signal from the interfering signals.

The particular base station may not be able to mitigate interferencefrom other base stations' user terminals on the uplink, or mitigatetowards other base stations' user terminals on the downlink. Theparticular base station may not have an adequate radio-frequency link tothe other user terminals or may not have information on how to poll theother base stations' user terminals.

Initiating Communication

When initiating communication with a remote user terminal, the remoteuser terminal may be logged off the system or may be in an “idle” statein which no communication is taking place or has taken place relativelyrecently between the base station and the user terminal, or in whichcommunication takes place at a relatively slow rate with substantialsilent periods.

Initiating communication between a base station and a user terminal thatmay be in an idle state can be relatively difficult. The location of auser terminal may be unknown because, for example, it is mobile.Furthermore, interference patterns may be rapidly varying, so that evenif the location is known, there may be considerable interference presentthat may reduce the likelihood of successful reception of the initiating(e.g., paging) message by the base station. Furthermore, the channel forpaging may be heavily used by user terminals of other base stations. Insuch cases, the interference to the desired/intended user terminal maybe considerable.

It is often desirable to page the user terminal on a conventionalchannel that may be heavily used on different spatial channels by otherremote terminals of the same base station. In such a case, theinterference to the user terminal may also be considerable.

Sending a paging message to page a user terminal is typically ideallycarried in some manner that increases the likelihood that a userterminal at an unknown and possibly changing location in an environmentwith rapidly varying interference will successfully receive such paging(and other control signals) from its associated base station.

SUMMARY

Disclosed herein are a method, apparatus, and machine-readable mediumfor transmitting a downlink signal in a substantially non directionalmanner from a communication station to a first remote communicationdevice on a downlink channel. The communication station includes a smartantenna system having an array of antenna elements. In one embodiment,the method includes determining a first downlink smart antennaprocessing strategy for transmitting in a first non-directional manner,transmitting a first downlink message from the communication station inthe first non-directional manner using the first downlink smart antennaprocessing strategy, and repeating transmitting the first downlinkmessage from the communication station in a second non-directionalmanner. The repeated transmitting is non-identical repetition tofacilitate the interference environment being different in therepetition.

One embodiment includes a method of paging a first remote communicationdevice on the downlink from a first communication station of acommunication system. The communication system includes at least none ormore other communication stations distinct from the first communicationstation, each associated with one or more other remote communicationdevices. The first communication station associated with at least afirst remote communication device, and including a smart antenna systemhaving an array of antenna elements. The method includes providing afirst set of sequential time intervals for the first communicationstation for communication with its associated remote communicationdevices, each time interval of the first set including a selected numberof downlink conventional channels. The method further includestransmitting a first paging signal from the first communication stationto the first remote communication device during a first downlinkconventional channel of a first time interval of the first set, andrepeating the transmitting at a time interval later than the first timeinterval, the repeated transmitting being of a second paging signal fromthe first communication station to the first remote communication deviceon a downlink conventional channel of the first set. The repeatedtransmitting step uses a strategy other than identical repetition tofacilitate the set of remote communication devices actively receiving onthe downlink on the first downlink conventional channel during the firsttransmitting step differing from the set of remote communication devicesactively receiving during the repeated transmitting step on the downlinkconventional channel used for paging during the repeated transmittingstep.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of a communication system that includes at least twobase stations, at least one base station having a smart antenna system.

FIGS. 2A and 2B illustrate two embodiments of a base station using asmart antenna system; FIG. 2A shows one configuration in which the smartantenna system is an adaptive antenna array system and adaptation occursin baseband. FIG. 2B shows an alternative base station with a switchedbeam smart antenna system that includes a beamforming network.

FIGS. 3A, 3B, 3C, 3D, and 3E illustrate signal timing arrangements inaccordance with half duplex embodiments of the present invention.

FIGS. 4A, 4B, and 4C illustrate signal timing arrangements in accordancewith a full duplex embodiment of the present invention.

FIGS. 5A, 5B, and 5C illustrate signal timing arrangements in accordancewith an alternate embodiment of the present invention.

DETAILED DESCRIPTION

A Cellular System and Its Smart Antenna Base Station

Referring to FIG. 1 there is generally shown a cellular wirelesscommunication system 100 having at least two base stations, a first basestation 102 and at least one second base station 111, with the firstbase station 102 including a smart antenna system that has an array ofantenna elements 104. System 100 also includes a plurality of remote,possibly mobile user terminals 105, 106, 107, and 108 for conductingbi-directional packet communications with first base station 102, and aplurality of remote, possibly mobile user terminals 109 and 110 forconducting bi-directional packet communications with the other basestations, such as second base station 111. First base station 102 issaid to be associated with user terminals 105, 106, 107, and 108, whilesecond base station 111 is associated with user terminals 109 and 110.

The first base station 102 is coupled to a network such as a data and/orvoice network. The one or more second base stations 111 may also becoupled to the same network. In one embodiment, the first base stationand other base stations 111 are coupled to the Internet.

FIG. 2A shows one embodiment of first base station 102. The base stationincludes a smart antenna system 203 that is an adaptive antenna arraysystem. Smart antenna system 203 has an array of antenna elements 104, aset of transmitters and a set of receivers, implemented in oneembodiment as a set of transmitter/receivers (“transceivers”) 206, withone transmitter and one receiver for each individual antenna element ofarray 104, and a spatial processor 208 for performing uplink anddownlink smart antenna processing.

Uplink smart antenna processing includes combining the signals receivedfrom the individual antenna elements via the set of transceivers, anddownlink smart antenna processing includes generating multiple versionsof a signal for transmission from the individual antenna elements viathe set of transceivers. A control computer 210 controls the smartantenna processing. Spatial processor 208 and control computer 210comprise one or more digital signal processing devices (DSPs); any othermechanisms for achieving the uplink and downlink smart antennaprocessing and control may be used.

On the uplink, the smart antenna processing is carried out under controlof the control computer 210 by weighting the received signals inamplitude and phase according to a set of uplink weighting parameters toadvantageously combine the received signals. Such combining is referredto as uplink spatial processing and uplink smart antenna processing. Theuplink smart antenna processing strategy, in this case, is defined bythe set of uplink weighting parameters. Such combining may furtherinclude temporal filtering for time equalization, and when combined withspatial processing, such combining is called uplink spatio-temporalprocessing or again, uplink smart antenna processing. Spatio-temporalprocessing is performed according to an uplink smart antenna processingstrategy defined by a set of uplink weighting parameters that includestemporal processing parameters for signals originating at each of theantenna elements. For simplicity, the terms uplink spatial processingand uplink smart antenna processing shall mean either uplinkspatio-temporal or uplink spatial processing herein.

The uplink strategy is typically determined based on signals received atthe antenna elements of the base station 102, and in one embodiment, thedownlink strategy is determined also based on the signals received atthe antenna elements.

Thus, in one embodiment, the base station 102 includes a downlinktransmission unit coupled to the antenna elements to transmit downlinkdata on a downlink channel to an associated remote user terminal, anuplink reception unit, coupled to the antenna elements to receive anuplink signal from the remote user terminal, and a processor, coupled tothe downlink transmission unit, and further coupled to the uplinkreception unit, the processor to determine a downlink smart antennaprocessing strategy based on the uplink response signal.

Note that while in one embodiment, the antenna elements 104 first basestation 102 are each used for both transmission and reception, inanother embodiment, the plurality of antenna elements include a separateantennas for reception and transmission.

A user terminal such as 105, 106, 107, 108 typically includes an antennasystem and a transceiver, and may be coupled to input and/or outputdevices and/or processing devices to provide various types offunctionality, such as voice communications and/or data communicationsover the Internet or other data communication network. Such a userterminal may be mobile or stationary. In one embodiment, the antennasystem may have a single antenna, or, in another embodiment, may includea plurality of antenna elements to facilitate diversity reception andtransmission. In yet another embodiment, the antenna system may includea smart antenna system. The user terminals, in one embodiment, may evenbe able to communicate voice and/or data between each other. Coupled to,or as part of the user terminal may be one or more of a computer such asa laptop computer, a two-way pager, a personal digital assistant (PDA),a video monitor, an audio player, a cellular telephone, or other devicethat may communication voice or data in a wireless fashion with anothercommunication device or communication station, such as a base station.

When a signal is received from one of the remote transmitters 105, 106,107, 108, the adaptive spatial processor 208 responds to the amplitudeand phase of the signals as received at each of the antenna elements ofarray 104 and performs uplink spatial processing that combines thesignals in a manner that effectively provides a directional receptionpattern that advantageously enhances the signal link from the userterminal to the base station, including compensation for multipathconditions that might exist, and providing interference mitigation.

Various techniques are known for determining the uplink smart antennaprocessing strategy as defined by the weighting parameters. In oneembodiment, a known training sequence of symbols is included in theuplink signal. One version of the embodiment uses a least squares methodfor the strategy determining. In another embodiment, a “blind” method isused, according to which a reference signal is constructed that has oneor more properties that the uplink signal is known to have, for example,a constant modulus or a particular modulation format. Either the knownsignal or the constructed reference signal is used to form an errorsignal, and uplink smart antenna strategy determining determines theuplink weighting parameters that optimize some criterion based on theerror. In one embodiment, the criterion is a least squared errorcriterion.

One embodiment may even operate in accordance with spatial divisionmultiple access (“SDMA”). With SDMA, more than one user terminalassociated with the first base station 102 can communicate with thefirst base station 102 on the uplink on the same “conventional” channel,that is, the same frequency and time channel (for an FDMA and TDMAsystem) or code channel (for a CDMA system), so long as the co-channelremote users are spatially separated. In such a case, the smart antennasystem provides for more than one “spatial channel” within the sameconventional channel, and the adaptive spatial processor 208 performsuplink spatial processing to mitigate interference from remote terminalsassociated with the first base station 102 that share the conventionalchannel with a desired user terminal.

The first base station 102 is also used to transmit a signal to one ormore of the remote units 105, 106, 107, 108 in a manner that effectivelyprovides a directional signal pattern that advantageously enhances thesignal link from the base station to the user terminal, includingcompensation for multipath conditions that might exist and mitigatinginterference. SDMA is also possible in the downlink direction,permitting the base station to transmit to more than one of itsassociated user terminals on the same conventional channel. That is, thesame conventional channel can have more than one spatial channel.

On the downlink, the spatial processor 208, under control of the controlcomputer 210, generates various versions of a signal to be transmittedto a remote terminal by weighting the signal in amplitude and phaseaccording to a set of downlink weighting parameters. Such processing isgenerally referred to as downlink spatial processing or downlink smartantenna processing. The downlink smart antenna processing strategy, inthis case, is defined by the downlink weighting parameters. Suchprocessing may further include temporal filtering for time equalization,and when combined with the weighting, such smart antenna processing iscalled downlink spatio-temporal processing. Downlink spatio-temporalprocessing is performed according to a downlink smart antenna processingstrategy defined by a set of downlink weighting parameters that includestemporal processing parameters for signals to be transmitted by each ofthe antenna elements. For simplicity, the term downlink spatialprocessing and downlink smart antenna processing shall mean downlinkspatio-temporal or spatial processing herein.

Various mechanisms are known for determining a downlink smart antennaprocessing strategy defined in this case by downlink weightingparameters. One embodiment operates in a communication system 100 thatis a TDMA system that uses time domain duplexing (TDD), so that theuplink and downlink frequency between a particular user terminal and itsassociated base station are the same. The downlink weighting parametersare typically determined from the uplink weighting parameters for thesame user terminal. Calibration factors are included in determiningdownlink weighting parameters from uplink weighting parameters tocompensate for the differences in distortion, for example, thedifferences in the amplitude and phase shifts that occur in the signalsas they pass through the different receive and transmit chains that arecoupled to each of the antenna elements of array 104. Such a chainincludes the antenna element, cables, filters, RF receiver, RFtransmitter, physical connections, and analog-to-digital converter ifprocessing is digital. U.S. Pat. No. 5,546,090, and U.S. patentapplication Ser. Nos. 08/948,772 and 09/295,434, each assigned to theassignee of the present invention, for example, include descriptions ofmethods and apparati for calibration.

In an alternate embodiment for operation in communication systems thatdo not use time domain duplexing, for example in an embodiment of theinvention operating in a system that uses frequency domain duplexing(FDD) in which the uplink and downlink frequencies for communicatingwith a particular user terminal are not the same, various techniques areavailable for determining the downlink weighting parameters from uplinksignals received from user terminals, including but not limited todetermining the directions of arrival (DOA) for the user terminals.

FIG. 2B shown an alternate embodiment of first base station 102 whichincludes a smart antenna system 223 that is a switched beam system.Smart antenna system 223 has an array of antenna elements 104, abeamforming network 225 that forms a set of fixed beams for the antennaelements of array 104, a set of transceivers 227, with onetransmitter/receiver for each individual beam terminal of beamformer227, and combiner 229 for combining one or more of the beams oftransceivers 227. An included control computer 231 controls the smartantenna system. Exemplary beamformers include but are not limited to, aButler matrix. The combiner 229 selects one or more of the fixed beamsto use on the uplink or downlink, and may include a switching network toselect the one or more beams. Combiner 229 may further include amechanism for combining the one or more beams. As with the adaptivesmart antenna system of FIG. 2A, the determining of how to control theswitched beam smart antenna system for downlink communication isreferred to as determining the uplink smart antenna processing strategy.The processing of combiner 229 during downlink communication is referredto as downlink spatial processing. On the uplink, the combining operatesby weighting selected beams according to a set of uplink weightingparameters to advantageously combine the received signals. As with theadaptive smart antenna system of FIG. 2A, such uplink combining isreferred to as uplink spatial processing, and determining thecombination for uplink communication is referred to as determining theuplink smart antenna processing strategy.

More particularly, when a signal is received from one of the remotetransmitters in remote units 105, 106, 107, 108, the beam combiner 229responds to the signals as received at each of the antenna elements ofarray 104 and performs uplink spatial processing that combines the beamsfrom beamformer 225 in a manner that effectively provides a directionalsignal pattern that enhances the signal link from the user terminal tothe base station, including compensating for multipath conditions thatmight exist and, in accordance to an aspect of the invention, mitigatinginterference.

Referring still to FIG. 2B, on the downlink, the combiner processes asignal to determine weighted versions to transmit via one or moreselected beams of beamformer 225. The processing of the combiner is toimprove the transmission from the base station to the user terminal,including compensating for multipath conditions that might exist and, inaccordance to an aspect of the invention, mitigating interference.

In both the embodiments of FIGS. 2A and 2B, in accordance with oneaspect of the invention, signals are also received from co-channelinterferers such as remote units 109 and 110 of other base station(s)111. The spatial processing uses these received signals in a manner thatmitigates interference from co-channel users such as remote units 109and 110 of other base stations 111.

Adaptive determining of a favorable smart antenna strategy, particularlyfor moveable user terminals or a multipath environment or for datacommunications in a computer network such as the Internet, or acombination of such factors, as in a cellular system, is best done atthe particular time of a data communication, because of the changing RFand interference environment. In the case of the remote user terminalbeing mobile, movement of the user terminal can result in the userterminal moving between a favorable and an unfavorable location betweensubsequent data transmissions. In the case of data transmission, forexample data transmitted between the user terminal and first basestation 102 when the communication system 100 is part of a computernetwork such as the Internet, the interference environment may bechanging rapidly. Thus, for the first base station 102, interferers suchas remote terminals 109 and 110 may be transmitting to their respectivesecond base station 111 at different times, and such an interferencepattern may change rapidly.

Initiating Communication from a Base Station

For initiating communication on the downlink from first base station102, in order to rapidly determine the optimum smart antenna processingstrategy, in accordance with one embodiment of the present invention,the first base station 102 transmits an initial downlink paging messageto the user terminal in an agreed-upon logical control channel toindicate that the first base station 102 wants to commencecommunication.

A user terminal may be not logged in, or may be in an idle state inwhich it is logged in and authenticated, but not in activecommunicational exchange with its associated base station, or in anactive state in which it is actively communicating with its associatedbase station. When a user terminal is in an idle state, both the basestation and user terminal are prepared to initiate communication.Furthermore, both the base station and its idle terminals haveinformation indicating the set of potential channel or channels for thebase station to page the user terminal, or for the user terminal toinitiate communication with the base station.

Note that a user terminal may have the ability to communicate on morethan one channel, and thus may be idle on one channel and active onanother. By idle is meant idle on the channel of interest. It should beappreciated that an idle user terminal may be not idle on otherchannels.

Sending a paging message to page a user terminal is desirably carriedout in some manner that increases the likelihood that a user terminal atan unknown and possibly changing location in an environment withrelatively rapidly varying interference will successfully receive suchpaging (and/or other control signals) from its associated base station.

One aspect of the invention entails transmitting a downlink signal in anon-directional manner, while simultaneously mitigating interferencetowards one or more user terminals known to the base station to beundesired user terminals, in that each of the one or more user terminalsmay receive one or more signals in the particular downlink channelduring the transmitting of the downlink signal.

Non-directional manner, as used herein, refers to not intentionallydirecting energy towards any particular user or users. In a sectorizedsystem, this means non-directional within the sector. Furthermore,substantially non-directional means also non-directional on the timeaverage when the overall transmission is broken up into a set ofrepeated transmissions, each possibly with a different strategy.

One aspect of the invention entails a method for reliably initiatingcommunication from a base station such as first base station 102 to aparticular user terminal in a wireless packet data system such as system100. The method is particularly useful for base stations that have asmart antenna system as will be explained below.

One embodiment of the method includes transmitting a relatively heavilyencoded, relatively low-rate paging message by first base station 102for the express reason of getting the user terminal to respond. Theencoding is one of the methods facilitating a relatively highprobability of detection at the user terminal. A low-rate signal is sentbecause not much information is being transmitted. The user terminaldetects and responds to the paging message. The response is then used bythe base station to acquire information about the communication link forsubsequent transmission. This information about the communication linkgenerally provides reliable and relatively high-rate (e.g., trafficdata) communication between the base station and the user terminal. Userterminals of other base stations may also be responding to theirrespective base stations on the same conventional channel, and suchresponses also may be used by first base station 102 to mitigateinterference to or from the interfering co-channel user terminal(s) inthe subsequent downlink or uplink transmissions.

Paging in a Downlink Channel that Shares Downlink Data Transmissionsbetween Multiple User Terminals

In one embodiment, a paging message may be sent in a logical controlchannel that can occupy the same conventional channel as other data suchas traffic data being communicated between first base station 102 andone or more user terminals.

Furthermore, the paging message may be sent from first base station 102in a logical control channel that can occupy the same conventionalchannel as other data such as traffic data or paging data beingcommunicated between other base stations and one or more user terminalsof such other base stations.

Furthermore, the paging message may be sent from first base station 102in a logical control channel that can occupy the same conventionalchannel as other user terminals associated with the first base station102 and other users of one or more other base stations.

One embodiment includes providing a unique paging sequence calledUT_Sequence for each user terminal. This sequence may be generated inmany ways. For example, the base station identification and/the userterminal identification numbers could be used as inputs to a PN sequencegenerator. The resulting bits are then modulated and the resulting I/Qbaseband sequence forms the UT_Sequence. Many other ways of generatingUT_Sequence are possible. For example, the user terminal identificationnumber could be encoded using a low-rate error correction code, and theencoded number scrambled by a XOR operation with the output of a PNsequence generator initiated with all of or part of the base stationidentification number. The UT_Sequences are such that the probability oftwo user terminals having the same paging sequence is relatively low,and, in one embodiment, a UT_Sequence is unique to each user terminal inthe system. In one embodiment, the UT_Sequence includes coding toprovide a very large degree of redundancy in order to increase thelikelihood of successful reception of a UT_sequence at the desired userterminal.

Each user terminal listens on an agreed upon logical control channel,attempting to detect its UT_Sequence. This logical control channel maybe a control channel, or, in accordance with an aspect of the invention,may be a conventional channel also used for traffic by other userterminals in the system.

The user terminal uses a user terminal sequence detection criterionuntil it successfully detects its UT_Sequence. One detection method usescorrelation, with the detection criterion including a correlationthreshold.

The first base station 102, in some agreed upon manner, has informationindicating on what channel or channels the desired user terminal islistening, and the base station transmits the UT_Sequence on thischannel. The channel or channels to listen to, for example, may beagreed upon during an initial exchange during registration (“loggingin”) of the user terminal with its associated base station, or may bepre-set. The first base station 102 determined a smart antennaprocessing strategy for its smart antenna system to increase theprobability of successful reception of the UT_Sequence by reducing thelikelihood that interference will prohibit communication.

Prior to paging, the first base station 102 may be receiving signals(“prior-to-paging received signals”) from one or more of its associateduser terminals during a time in which the to-be-paged user terminal isidle and thus known to be not transmitting, but during which time anyuser terminal or terminals associated with first base station 102 thatmay be receiving data from first base station 102 at the same time andon the same conventional channel as the paging message, are transmittingon the uplink to first base station 102.

The first base station 102 uses the prior-to-paging received signals todetermine a downlink smart antenna processing strategy for its smartantenna system to transmit simultaneously the data to such co-channeluser terminals and the paging message on different spatial channels ofthe same conventional channel.

In addition to receiving signals from its associated user terminals, thefirst base station 102 may be receiving signals from interferers. Thefirst base station 102 distinguishes signals from its own associateduser terminals from the signals from interferers. In one embodiment thedistinguishing uses a user terminal identifier.

Note also that there may be no other user terminals associated with thefirst base station 102 that may be sharing the downlink conventionalchannel with the paging message.

One or more other base stations also may be included in communicationsystem, and in one embodiment, the other base station(s) are coordinatedwith first base station 102, such that in addition to first base station102 receiving the prior-to-paging received signals, the first basestation 102 may receive signals (“other-user-terminal receivedsignals”), prior to paging the to-be-paged user terminal, from one ormore other user terminals associated with the other base station(s), theother user terminals including being those that may be transmitted toduring, and on the same conventional channel as the paging message.First base station 102 distinguishes signals from its associated userterminals signals from signals from the other user terminal(s)associated with the other base station(s). Note that the other userterminal(s) associated with the other base station(s) may be receivingdata from their respective associated base station(s) at the same timeand the same conventional channel as the paging from first base station102.

Each base station uses a protocol to communicate with its associateduser terminals, so that two base stations being coordinated includesthat the protocols used by the base stations are coordinated.

The first base station 102 uses the prior-to-paging received signals andthe other-user-terminal received signals to determine a downlink smartantenna processing strategy for its smart antenna system to transmitsimultaneously data to its associated co-channel user terminals and thepaging message on different spatial channels of the same conventionalchannel, while mitigating interference to the user terminal associatedwith first base station 102 and to the other user terminals(s) fromwhich it received the other-user-terminal received signals.

In accordance with one embodiment, the downlink smart antenna processingstrategy determining uses downlink weighting parameters determined fromuplink weighting parameters by using calibration. The uplink weightingparameters are determined from signals received at the antenna elementsof the antenna array that correspond to the prior-to-paging receivedsignals and the other-user-terminal received signals.

In one embodiment, the smart antenna processing strategy determininguses the transmit covariance matrix determined, using calibration, fromthe receive covariance matrix of the signals received at the antennaelements of the antenna array that correspond to the prior-to-pagingreceived signals and the other-user-terminal received signals. Inparticular, the strategy includes interference mitigation using theinterference covariance matrix for signals arriving from interferingremote users.

Let Z_(R) be the m by n matrix of received signals on the antennaelements for all signals received at the base station from itsassociated user terminals in the conventional channel to be used forpaging, with each row being a vector of n complex valued (I and Qvalues) samples of the signal received in one of the m antennas. Letz_(R) be the m by 1 vector of complex random variables (I and Q values)representing the signal and noise received in each of the m antennas.The receive covariance matrix is defined as R_(R)=E[z_(R)z_(R) ^(H)]where E[.] is the expectation operation and the superscript H representsthe complex conjugate transpose operation, that is, the Hermitiantranspose, so that for m antenna elements, the receive covariance matrixR_(R) is an m by m matrix. In the absence of any desirable uplinksignals, that is, if only interference is present in a channel as wouldoccur when the desired user terminal is in an idle state, the receivecovariance matrix is the receive interference covariance matrix definedas R_(RI)=E[z_(RI)z_(RI) ^(H)] where z_(RI) is the vector of complexvalued (I and Q values) random variables of signals arriving at one ofthe m antenna elements of the antenna array from the transmittinginterfering remote terminals.

The received interference covariance matrix contains information aboutthe average spatial behavior of the interfering remote terminals. Theeigenvectors of this matrix define the average spatial directionoccupied by the interference. The eigenvalues of the receivedinterference covariance matrix indicate the average power occupied bythe interference in each of the eigenvalue directions. Thus, eigenvectordirections that are associated with relatively large eigenvaluesindicate spatial directions that receive a relatively large amount ofaverage interference power while the eigenvector directions associatedwith relatively small eigenvalues indicate spatial directions thatreceive relatively less average interference power.

In one embodiment, the expectation operation is carried out by averagingover the samples of the signals. That is, R_(R)=Z_(R)Z_(R) ^(H) andR_(RI)=Z_(RI)Z_(RI) ^(H) where Z_(RI) is the m by n matrix of receivedsignal samples on the antenna elements for signals received at the basestation absence of any desirable uplink signals, again with each rowbeing a vector of n complex valued (I and Q values) samples of thesignal received in one of the m antennas.

In one embodiment, the receive covariance matrix is used to determine afavorable downlink processing strategy that includes mitigatinginterference towards undesired co-channel user terminals. When some ofthe set of co-channel user terminals transmitting during the calculationof the receive co-variance matrix are also receiving when the first basestation transmits, such a strategy is relatively effective for achievingthe interference mitigation.

In accordance with one aspect of the invention, prior to paging, thereceived interference covariance matrix is determined by sampling duringa time in which the to-be-paged users are known to be not transmitting(e.g., in the idle state), but during which the undesired user terminalsthat may be receiving on the downlink at the same time and on the sameconventional channel as the paging message may be transmitting on theuplink to their respective base station.

Alternatively, the interference covariance matrix may be determined fromperforming uplink spatial processing on signals received at first basestation 102 at a time in which both the to-be paged user terminals andthe other user terminals—those that may later be receiving on thedownlink on the same conventional channel and time as the paging—may betransmitting. The uplink spatial processing determines the signals fromthe to-be-paged user terminals, and subtraction determines theinterfering signals.

The receive covariance matrix is determined from signals (e.g., theprior-to-paging received signals and the other-user-terminal receivedsignals) received by first base station 102 at a time when the potentialco-channel remote terminals are likely transmitting data and when thedesired user terminal is idle. This receive covariance matrix is equalto the receive interference covariance matrix, and may be used toadvantageously determine the smart antenna processing strategy forreceiving signals, including interference mitigation from theinterfering transmitters.

The transmit spatial processing for paging, including interferencemitigation towards undesired user terminals, can thus be determined fromthe receive interference covariance matrix determined when the undesireduser terminals are transmitting on the uplink, provided calibration oranother operation is performed to account for the differences in theelectronic apparatus chains to and from the different antenna elements.In particular, the set of downlink weighting parameters for downlinkspatial processing for transmitting the paging are taken from theeigenvectors of the received interference covariance matrix that have arelatively small value, preferably but not necessarily the smallestvalue.

Note that as described further below, in accordance with one embodiment,active traffic communication between the base stations of system 100 andits associated user terminals occurs in sets of sequential timeintervals (frames), and each frame is divided into a selected number ofdownlink conventional channels (e.g., time periods for a TDMA system).For each downlink conventional channel, there is an associatedacknowledgement conventional channel (e.g., time period for a TDMAsystem) on the uplink. The description hereinafter will generally applyto one embodiment of the invention used in a TDMA system, but theinvention is not limited to TDMA systems.

In a TDMA system, each frame is divided into a selected number ofdownlink data transfer periods (timeslot), and for each downlink datatransfer period, there is an associated acknowledgement transfer period(timeslot) on the uplink. After communication is established betweenfirst base station 102 and a desired user terminal, a downlink datatransmission from first base station 102 to the user terminal ispreceded by an acknowledgement signal from that user terminal during anearlier associated acknowledgement transfer period, preferably but notnecessarily, the most recent acknowledgement transfer period on theuplink associated with the downlink data transfer period of the downlinkdata transmission. The acknowledgement signals received on the uplinkare used to advantageously determine a processing strategy for the smartantenna system of first base station 102 to transmit to the desired userterminal in a future—preferably but not necessarily, the next—downlinkdata transfer period associated with the acknowledgement transferperiod. Furthermore, the sets of sequential time periods used by basestations are coordinated so that other acknowledgements from interferinguser terminals of the same or other base stations are also received atfirst base station 102 and used to determine the smart antennaprocessing strategy. Thus, the number of user terminals of thecommunication system 100 transmitting to their respective base stationsduring an acknowledgment period on the uplink is a superset of the setof active desired user terminals that may be transmitted to during theassociated future—preferably but not necessarily, next—downlink datatransfer period.

In one embodiment for transmitting a paging message to an idle userterminal during a particular downlink data transfer period, the downlinksmart antenna processing strategy is determined using calibration andthe eigenvector having the smallest eigenvalue of the covariance matrixdetermined from signals received during the previous associatedacknowledgement transfer period on the uplink.

Using such a paging strategy includes interference mitigation to thoseuser terminals from which signals (e.g., the prior-to-paging receivedsignals and the other-user-terminal received signals) were received bythe first base station 102 during the previous associatedacknowledgement transfer period on the uplink. The eigenvectors of thereceive covariance matrix corresponding to such received signals fromtransmitting user terminals would have eigenvalues significantly largerthan the smallest eigenvalue. Thus, in one embodiment, the pagingmessage is sent in the direction of what was the least powerfulinterferer on the uplink to minimize interference towards co-channelusers.

In alternative embodiments, an eigenvector of the transmit(interference) covariance matrix that has a value less than a providedthreshold may be used for determining the downlink smart antennaprocessing strategy (e.g., the downlink weighting parameters) to use forpaging. Such an eigenvector is substantially in the null space of thetransmit interference covariance matrix.

Our definition of transmitting in a non-directional manner as referredto herein includes null space transmitting which “directs” energy in thedirection of relatively small eigenvectors of the convariance matrix.

In yet another alternate embodiment, the receive signal covariancematrix determined at a time when the potential co-channel remoteterminals are likely transmitting data and when the desired userterminal is idle, is used with calibration to expressly direct nulls inthe direction of undesired co-channel users while transmitting thepaging message in other directions according to an omnidirectionalradiation pattern. An omnidirectional pattern is a special case oftransmitting in a non-directional manner. In a sectorized system,omnidirectional means substantial omnidirectional within the sector.Furthermore, substantially omnidirectional means also substantiallyomnidirectional on the time average when the overall transmission isbroken up into a set of repeated transmissions, each possibly with adifferent strategy.

U.S. patent application Ser. No. 08/988,519 to Goldburg, filed Dec. 12,1997 and assigned to the assignee of the present invention, provides adescription of one method to determine downlink spatial processingweighting parameters to achieve any desirable radiation pattern. Inaccordance to the Goldburg method, the weights are determined byoptimizing an optimality criterion. For the alternate embodiment of thepresent invention, the Goldburg method can be modified to includedirecting nulls towards the likely interferers as determined from thecovariance matrix.

Alternatively, a direction-of-arrival (DOA)-based method may be used todetermine the downlink smart antenna processing strategy.

An alternate method of mitigating interference towards the undesireduser terminals include forming side information about the undesired userterminals from signals received at first base station 102 from theundesired user terminals at some earlier time. The side information maybe stored in a database in first base station 102.

Side information about an undesired user terminal is information aboutthe user that can be used to determine a strategy that includesmitigating interference towards the undesired user terminal. An exampleof such stored side information about a user terminal is the spatialsignature of the user terminal. For example, U.S. Pat. No. 5,592,490 toBarratt, et al., entitled “SPECTRALLY EFFICIENT HIGH CAPACITY WIRELESSCOMMUNICATION SYSTEMS,” and U.S. Pat. No. 5,828,658 to Ottersten, etal., entitled “SPECTRALLY EFFICIENT HIGH CAPACITY WIRELESS COMMUNICATIONSYSTEMS WITH SPATIO-TEMPORAL PROCESSING,” provides a description of sometechniques to mitigate interference using spatial signatures. Thereceive spatial signature characterizes how the base station arrayreceives signals from a particular user terminal in the absence of anyinterference or other user terminals. The transmit spatial signature ofa particular user terminal characterizes how the remote user terminalreceives signals from the base station absence of any interference. Atransmit spatial signature may be determined from a receive spatialsignature using calibration.

The side information is retrieved from the database and used todetermine a smart antenna processing strategy to include interferencemitigation towards at least one of the undesired user terminals.

The side information may be formed from signals received from theundesired user terminals at the same first base station 102.Alternatively, the communication system may include at least one secondbase station and an inter-base-station communication mechanism, whichmay be hard-wired and/or wireless. One or more other base stationsreceive the signals from the undesired user terminals, and the sideinformation forming step for each undesired user terminal occurs at theother base station receiving the signal from such each undesired userterminal. The side information is communicated to first base station 102using the inter-base-station communication mechanism. When such a methodis used, the other such base station communicates to first base station102 which of the undesired users are “really” undesired.

Other forms of side information include DOA of the one or more undesireduser terminals, and indeed, received signals from the undesired userterminals.

While one embodiment embodies a method that operates in a TDD system,the invention is also applicable for operation in a FDD system. In a FDDsystem, the transmit and receive channels are in general not correlatedwith one another at any given instant in time. DOA-based techniques maybe used for determining the downlink smart antenna processing strategyfrom the directions of arrival of user terminals. Furthermore, thetransmit and receive covariance matrices are typically substantiallyequal in an FDD system when sufficient time averaging is used in thecalculation of the received covariance or interference covariancematrix, particularly when the uplink frequency is relatively close tothe downlink frequency. In such a case, using a downlink spatialprocessing strategy determined from the uplink spatial processingstrategy, including calibration, may provide satisfactory results, asdescribed, for example, in PCT International Patent ApplicationPublication No. WO 98/09385 published Mar. 5, 1998, to Clarity Wireless,Inc., Raleigh, et al., inventors, entitled “SPATIO-TEMPORAL PROCESSINGFOR COMMUNICATION.”

The invention is also applicable to CDMA systems. Often, CDMA systemsprovide substantially all the resources in a frequency channel to asmall number of user terminals. Thus, the eigenvalues related toeigenvectors of the receive covariance matrix corresponding totransmitting user terminals will be significantly larger than thesmallest (i.e., null space) eigenvalues.

Thus, one embodiment of the invention allows a base station to send adownlink message to a desired user terminal in a non-directional manner(e.g., page a remote terminal) such that interference to the other userterminals is simultaneously mitigated. Furthermore, in one embodiment,the first base station 102 simultaneously sends other data to one ormore other user terminals. Thus, on embodiment of the invention alsoprovides for combining directed traffic (such as ongoing traffic data)and broadcast traffic (such as a page) over the same conventionalchannel.

Repetitive Paging

In response to successfully receiving a paging messages, the userterminal transmits a signal to the first base station 102. The userterminal responds by sending a random access request signal to the basestation in an agreed upon channel. The first base station 102 thentransmits an access assignment message to the user terminal thatincludes designating a frequency channel and a downlink transfer timeperiod for the traffic communication. The access assignment message maybe used also to carry out several control functions, including measuringthe path loss in the link between the user terminal and the base stationand/or for performing power control.

The paging message is preferably but not necessarily relatively heavilycoded. Many methods are available for detecting such heavily codedUT_Sequences from signals received at the user terminal's receiveantenna. One such technique uses correlation.

The random access request signal is thus an indication to the first basestation 102 that the desired user terminal has successfully detected itsUT_Sequence. In one version, the absence of a random access requestsignal provides feedback to base station 120 that the desired userterminal has not successfully received the page. Other methods ofproviding feedback of success or failure also may be used in otherembodiments of the invention.

Thus, in one embodiment, the first base station 102 receives feedbackthat indicates whether or not the desired user terminal has successfullyreceived a page.

Another aspect of the invention is a method to further increase thelikelihood of successful page reception detection by repeating thetransmission of the page one or more times using identical repetition,i.e., using an identical downlink strategy in the same relative timepart of a future frame in a repeating manner. Non-identical repetitionrefers to one or more of the downlink strategy or the relative time partof the future frame being different. In one embodiment, non-identicalrepetition is used to facilitate the interference environment beingdifferent in the repetitions and thus to increase the cumulativelikelihood that the desired user terminal successfully receives the pageover the likelihood in the case of identical repetition. For example, adifferent smart antenna strategy may be used, or different timing may beused to increase the likelihood that the interference environment isdifferent. Downlink strategy diversity is provided by using a differentdownlink smart antenna strategy, or interference diversity is providedby repeating the page in a different interference environment. In oneembodiment, both downlink strategy diversity and interference diversityare used.

In one embodiment, the feedback of success or not in paging is used.After a first unsuccessful page, the base station repeats the page in afuture—e.g., the next—frame using, in one embodiment, a differentnon-directional downlink strategy.

In a first embodiment, the different non-directional strategy transmitstowards another one of the eigenvectors that is substantially in theinterference covariance matrix null space to determine a smart antennaprocessing strategy for downlink paging. Repeating in a future frame ofthe sequence of frames may provide for paging in the presence of adifferent set of interferers since the interference environment may berapidly changing, for example because a different set of user terminalsmay be being paged in the next frame. Using a different eigenvector inthe null space directs the page over a different radiation pattern,providing downlink strategy diversity.

The interference environment may not change sufficiently rapidly. Thus,in a second embodiment, the repetition is carried out in a differentdownlink data transfer period of the set of sequential time periods. Inthe case of TDMA, for example, this may coincide with a differenttimeslot. To generalize, the repeated transmission occurs on a differentdownlink conventional channel than the particular downlink traffic datatransfer conventional channel of first transmission. For a FDMA system,this may be a different frequency.

Thus, in accordance to the second embodiment, the receive interferencecovariance matrix is determined from signals received at anacknowledgement transfer period that is associated with a differentdownlink data transfer period, and the eigenvector of the receivedinterference covariance matrix with the smallest eigenvalue is used todetermine the downlink spatial processing for the smart antenna systemduring transmission of the page during this different downlink datatransfer period to facilitate repetition of the page in a differentinterference environment.

Alternate embodiments carry out the repeated paging with downlinkstrategies that are not necessarily determined from the interferencecovariance matrix. In yet another embodiment, the page towards aparticular user terminal is repeatedly transmitted using a different oneof a sequence of sets of weighting parameters for the smart antennasystem designed to increase the probability that a user terminal at anunknown location receives the page. For example, U.S. patent applicationSer. No. 09/020,619 to Barratt, et al., filed Feb. 9, 1998, and assignedto the assignee of the present invention, describes techniques fordetermining such a sequence. The sequence of weighting parameters usedto in the smart antenna processing strategy to sequentially transmit themessage is, according to one embodiment, an orthogonal sequence ofcomplex valued weighting parameter sets based on the discrete Fouriertransform (DFT). In order to further increase the chance of successfulreception of the page, the repetitions of page transmission occur duringdifferent downlink data transfer periods to facilitate repetition of thepage in a different interference environment.

In another embodiment using page repetition, pages are each transmittedwith a broad, e.g., omnidirectional beam, but again during eachdifferent repetition the pages are transmitted during different downlinkdata transfer periods (e.g., different timeslots) to ensure that therepeating pages occur in different interference environments. The methodof transmitting with an omnidirectional pattern is as described, forexample, in above-referenced U.S. patent application Ser. No. 08/988,519to Goldburg.

In one embodiment, each downlink data transfer period is divided intotwo halves for the purpose of paging. A page can be sent on the firsthalf or the second half of any downlink data transfer period. Thisprovides for relatively more paging messages possible within a givennumber of downlink data transfer periods. This also provides yet anothermethod for changing the interference environment between repetitions ofthe page. After a page is sent in one half of a downlink data transferperiod, the next repetition is sent in the other half of the nextframe's downlink data transfer period, in one embodiment a differentdownlink data transfer period. Thus, the interference environment, atleast with respect to paging transmissions, may change between the firstand the second transmission.

Other embodiments may include splitting the downlink data transferperiod into more than two paging periods.

FIG. 3 shows the sequence of frames for an embodiment of the inventionused with TDMA. FIG. 3A shows three complete frames. FIG. 3B shows asingle (the Nth) frame, and FIG. 3C shows how the downlink data transferperiods, in this case period D3, are divided into a first and secondhalf for the purpose of paging. Similarly, FIG. 4 depicts an alternate,full duplex arrangement. FIG. 4C shows how the downlink data transferperiods, in this example, the period D3, are divided into a first andsecond half for the purpose of paging.

In one embodiment of the invention, the number of repetitions is afunction of an estimate of the proximity of the desired user terminal tothe paging base station. The proximity of the user terminal is estimatedduring an initial registration (e.g., log-in), or during a previoussuccessful paging sequence. It is generally, but not necessarily,assumed that a user terminal estimated to be near the paging basestation experiences less interference than a user terminal estimated tobe far away. In one embodiment, the estimated closeness is one of near,far, and very far, and a near user terminal receives one page, i.e., norepetitions, a far user terminal receives two pages, i.e., onerepetition, and a very far user terminal receives two repetitions.

However, alternate embodiments may use other criteria for determiningvarious numbers of repetitions. A method for repeating transmitting apage from a base station having a smart antenna system to a userterminal using the smart antenna system, such that each repetitionoccurs in different interference environments has been disclosed inaccordance with at least one embodiment of the invention.

Traffic Communication

In one embodiment of the invention, traffic communication between thebase station and its associated user terminals occurs according to aradio protocol. The radio protocol provides a first set of sequentialtime intervals (frames) for first base station 102 to communicate withits associated user terminals. The radio protocol also provides furthersets of sequential time intervals (frames) for each of a set of otherbase stations 111 of the wireless communication system.

FIG. 3 depicts a set of transmission time diagrams illustrating thetransmission sequences in the case of one TDMA embodiment. FIG. 3A showsthe overall division of time into a sequence of contiguous frames, inone embodiment having equal duration. Three complete sequential framesare illustrated in FIG. 3A. For purposes of system timing control, asynchronization channel which user terminals may consult as needed, isprovided. In an alternate embodiment, each signalling segment startswith a frame marker signal from the base station to synchronize allremote user terminals to the timing sequence of the base station.

One aspect of the present invention relates primarily to thearrangements of signals within each frame, and accordingly an exemplaryframe (frame N) is shown in greater detail in FIG. 3B, together with theend of the previous frame (frame N−1) and the start of the next frame(frame N+1).

The frame in accordance with one TDMA embodiment of the invention issubdivided into a selected number of downlink data transfer periods(timeslots) D1, D2, D3, etc., and a selected number of uplink datatransfer periods (timeslots) U1, U2, etc. There also is a number ofacknowledgement transfer periods (timeslots) AKD1, AKD2, AKD3, etc., onthe uplink, one associated with each downlink data transfer period andhaving a predefined relationship to its associated downlink datatransfer period known to the base station and, in one embodiment, fixed.There also is a number of acknowledgement transfer periods (timeslots)AKU1, AKU2, etc. on the uplink, one associated with each uplink datatransfer period and having a predefined relationship to its associateduplink data transfer period known to the base station and, in oneembodiment, fixed. For one TDMA embodiment, the fixed relationshipbetween a data transfer period and its associated acknowledgementtransfer period is specified by timeslots. That is, the particulartimeslot for the data traffic period determines the timeslot for theassociated acknowledgement transfer period in the opposite direction.Furthermore, in one embodiment, this relationship is the same for allsets of sequential time periods for all base stations of the system.

Note that for a TDMA embodiment, each data transfer periods correspondsto a conventional channel.

In the example illustrated in FIG. 3B, there are four downlink datatransfer periods, thus four uplink acknowledgement transfer periods, andtwo uplink data transfer periods, and thus two downlink acknowledgementtransfer periods. Recalling that SDMA facilitates more than onecommunication channel called spatial channels during the same timeslot,the example of FIG. 3B corresponds to accommodating at least four activeuser terminals communicating on the downlink and at least two activeuser terminals communicating on the uplink.

One feature of the sequence of time intervals is that it can accommodatea different number of data transfer periods on the uplink and on thedownlink. In data communication, for example when the base station iscoupled to a computer network such as the Internet, there typically ismore communication on the downlink than on the uplink. One aspect of theinvention is accommodating the asymmetry between uplink and downlinktraffic data communication. A system may include a greater or lessernumber of each type of period shown herein depending on the number ofactive user terminals to be accommodated in a particular channel and thedata transfer requirements and capacities of the system in eachdirection. For higher data transfer rates, a larger number of users inany direction can be accommodated by various embodiments of theinvention.

In one alternate embodiment, the same number of uplink and downlink datatransfer periods exist in each sequential time interval, so that thetotal data carrying capacity of the set of provided downlink trafficchannels is the same as the total data carrying capacity of the set ofprovided uplink traffic channels.

Downlink Traffic Communication

After a successful page, the access assignment message from first basestation 102 assigns a downlink transfer period (i.e., a downlink trafficchannel) and an associated acknowledgment transfer period (i.e., anassociated uplink channel) within each sequential time interval in thefirst set of sequential time intervals.

Each user terminal that is successfully paged (e.g., that received anaccess assignment message as a result of initial downlink paging fromits associated base station) responds to the paging sequence (e.g., tothe access assignment message) on the uplink at the acknowledgementtransfer period corresponding to its assigned downlink traffic transferperiod. The first and further sets of sequential time intervals are suchthat the responses of the user terminals on the uplink to the initialdownlink paging sequence (e.g., to the access assignment message),including responses from user terminals of other base stations such assecond base station 111, occur on acknowledgement conventionalchannels—e.g., transfer periods and frequency/code channels—known tofirst base station 102. In particular, in one TDMA embodiment, thetimings of base stations are synchronized, and the responses of anydesired user terminals are aligned in time with possible responses ofany interfering user terminals such as other co-channel user terminalsassociated with the first base station 102 or of other base stations 111that may occur in the same frequency channel and downlink data transferperiod.

The acknowledgement signal from the user terminal to its associated basestation may include some training data and some identificationinformation. In one embodiment, the training data includes theidentification information. The identification information facilitatesthe first base station 102 to distinguish signals from its ownassociated user terminals from signals from user terminals of other basestations. The identification information may include a base stationidentifier. The first base station 102 receives the responses (i.e., theacknowledgments) and uses the training data and identifying informationto determine a smart antenna processing strategy for transmitting dataduring a future—in one embodiment the next—downlink data transfer periodfor the user terminal.

A desirable smart antenna processing strategy of first base station 102for transmitting the downlink traffic data to the user terminal isdetermined to include interference mitigation directed towards theco-channel interferers so that such interference from the transmittingbase station towards such other co-channel user terminals is mitigated.Furthermore, a desirable smart antenna processing strategy for receivingthe acknowledgment signals from the user terminal is determined in oneembodiment to include interference mitigation from co-channelinterferers.

In one embodiment, the acknowledgment includes an acknowledgment message(ACK) to provide feedback to the base station of successful reception atthe user terminal of the signal from the base station. When the basestation does not receive an expected ACK, or is fed back informationthat the message was not successfully received, the base stationreschedules transmission of the data.

The first base station 102 now transmits data (i.e., traffic data) tothe user terminal in the designated downlink data transfer period. Theactive user terminal receives the downlink traffic data transmitted toit from first base station 102. In one embodiment, the downlink signaltransmitted to the user terminal, in addition to communicating thetraffic data, also acts as a downlink polling signal to obtain aresponse on the uplink for determining the smart antenna processingstrategy for further communication. Thus, in response to the downlinktraffic data, during the next acknowledgement transfer period on theuplink for the designated downlink data transfer period, the userterminal transmits an acknowledgement signal back to the base station.The base station receives this acknowledgement, and alsoacknowledgements from one or more co-channel interfering user terminalsthat are assigned to the same downlink data transfer period, and usesthese signals received from the user terminals to determine the smartantenna processing strategy to advantageously transmit data to the userterminal during the next designated downlink data transfer period forthe user terminal. The determined downlink smart antenna processingstrategy includes interference mitigation towards the co-channel remoteterminals of other base stations 111. Furthermore, the first basestation 102 also determines a processing strategy for its smart antennasystem to advantageously receive the acknowledgment signals from desiredand interfering co-channel remote terminals in a manner that includesinterference mitigation from the interfering co-channel users. When thesystem, in accordance with one embodiment of the invention, alsoprovides for more than one spatial channel in the same conventionalchannel, e.g., the same timeslot in a TDMA system, the determined smartantenna processing strategy includes interference mitigation for theco-channel interfering remote terminals of the same base stations 102 onother spatial channels of the same conventional channel.

Note that at a given acknowledgment transfer period for receivingacknowledgement signals from user terminals, the first base station 102receives acknowledgments from user terminals which may be in response toa paging sequence (e.g., an access assignment messages) or to downlinktraffic data.

Once downlink data transfer is so initiated, the downlink traffic datatransfer continues at the designated downlink data transfer period frameby frame. Each downlink data signal also acts as a downlink pollingsignal. The user terminal receives the downlink data from its associatedbase station at the designated downlink data transfer period, and sendsan acknowledgement signal back to the base station during the nextdesignated acknowledgement transfer period. The acknowledgement signalis received at the base station, together with any other acknowledgementsignals from other co-channel user terminals of the same or other basestations, and again the base station determines a processing strategyfor its smart antenna system for optimally receiving theacknowledgements and for optimally transmitting the next downlink datasignal at the next designated downlink data transfer period. Byoptimally is meant using a downlink strategy that mitigates interferencefrom and towards interfering user terminals from which the first basestation 102 receives acknowledgements while enhancing communication withone or more desired user terminals.

Thus, in the case that the smart antenna processing strategy determininguses signals received during a particular acknowledgement transferperiod and is used for transmitting data during the next downlink datatransfer period associated with the particular acknowledgement transferperiod, the set of active user terminals being transmitted to duringthis next downlink data transfer period is a subset of the set of userterminals transmitting to their respective base station during theprevious particular acknowledgement transfer period. In one embodiment,only a user terminal from which a signal was received at the previousparticular acknowledgement transfer period is transmitted to on thedownlink at the next associated downlink data transfer period. Thus, anactive (i.e., not in the idle state) user terminal that is beingtransmitted to from a base station on a particular one of the downlinkdata transfer periods is known to have first transmitted data to thebase station on a previous acknowledgement transfer period on the uplinkassociated with the same particular downlink data transfer period.

Initiating Uplink Communication from a User Terminal

According to another aspect of the invention, initiating communicationon the uplink from one of the user terminals associated with the firstbase station 102 is provided. When the user terminal attempts toinitiate data transmission to first base station 102, the user terminalfirst transmits a random access request signal on an agreed-upon logicalcontrol channel, and this random access request is received by the firstbase station 102. In response, the first base station 102 transmits anaccess assignment message to the user terminal, also on an agreed uponlogical control channel, including transmitting information to the userterminal to indicate to the user terminal that the random access requestsignal has been received, and also including data to designate theuplink data transfer periods and frequency channel for receiving a datatransfer on the uplink from the user terminal.

The user terminal, in response, sends the uplink traffic data during thedesignated uplink traffic transfer period. The base station receives theuplink data from the user terminal. User terminals of other basestations such as second base station 111 may also be transmitting uplinktraffic data to their respective base stations, and these signals mayinterfere with the uplink traffic signal to first base station 102.Furthermore, when first base station 102 also provides for SDMA, itsassociated other user terminals that share the conventional channel mayalso so interfere. In accordance with one embodiment of the invention,the uplink data acts as a response to the access assignment message fromthe base station, and provides for the first base station 102 to use theresponse (i.e., the uplink traffic data) to determine a smart antennaprocessing strategy for reception of signals from the user terminal. Inaccordance with this one embodiment, the first and further sets ofsequential time intervals are designed so that the uplink trafficsignals are sent—either in response to the access assignment messages oras continuing uplink traffic data—at uplink conventional channels—e.g.,data transfer periods and frequency/code channels—known to first basestation 102. The first base station 102 receives the uplink trafficsignals using a smart antenna processing strategy determined fromreceived signals. The smart antenna processing strategy is for receivingdata signals from its active associated user terminals. In oneembodiment, each uplink traffic data signal within a designated uplinkdata transfer period includes training data to provide information tothe base station for determining a processing strategy for the smartantenna system. The training data may include identificationinformation. In one embodiment, a control computer provides foradaptation, such that the smart antenna processing strategyadvantageously receives the uplink data within the same uplink datatransfer period. In alternate embodiments in which the control computerdoes not have sufficient computational power to determined the uplinksmart antenna processing strategy rapidly enough to optimally receivedata for the same uplink data transfer period, the uplink strategydetermining from data received within one uplink data transfer period isused by the smart antenna system to receive data at a future frame'suplink data transfer period, at a future—e.g., the next—uplink datatransfer period for the particular user terminal. In a TDMA embodiment,the timings of base stations are synchronized, and the uplink datatransfer periods of the desired user terminals and of interferingco-channel user terminals for transmitting to such user terminals'respective base stations may occur at the same timeslot and in the samefrequency channel.

In one embodiment, when the base station successfully receives theuplink traffic data from an active user terminal, it transmits anacknowledgement signal to the user terminal during a designatedacknowledgement transfer period on the downlink for the uplink datatransfer period. The uplink traffic data signal is thus used as areverse polling signal from the user terminal, and the response to thisis the acknowledgement signal from the base station, which, aftercommunication commences, can be considered as a reverse pollacknowledgement signal. The response to the further reverse pollacknowledgement signal (i.e., to the acknowledgement from the basestation) may be used by the base station to further determine aprocessing strategy for its smart antenna system.

In one embodiment, in order to increase the likelihood that theacknowledgement on the downlink is successfully received at the userterminal, the first base station 102 uses the uplink traffic data thatis being acknowledged to determine a processing strategy for its smartantenna system to advantageously transmit the acknowledgment to the userterminal at the next designated acknowledgment period on the downlink.The determined strategy includes interference mitigation towards one ormore co-channel user terminals of other base stations or the first basestation 102 from which uplink traffic data is received by the first basestation 102.

In one embodiment, an acknowledgment signal sent to the user terminalfrom first base station 102 also provide the user terminal with anacknowledgment message (ACK) as feedback of successful reception at thebase station. The acknowledgement message may also be a negativeacknowledgement message (NACK) or other such feedback. When the userterminal either receives a NACK or does not receive an expected ACK, oris somehow fed back information that the message was not received, theuser terminal reschedules transmission of the data. Furthermore, theacknowledgment signal may include training data to aid in successfulreception at the user terminal. Furthermore, in one embodiment, one ormore user terminals may include a smart antenna system, and in such acase, the acknowledgements on the downlink to uplink traffic may also beused to determine a smart antenna processing strategy for the smartantenna systems of the user terminals.

Uplink communication from the user terminal to the first base station102 may continue frame-by-frame at the designated uplink data transferperiods. Each uplink data received by the base station may be used,together with any co-channel uplink traffic data from other interferinguser terminals, to determine a processing strategy for the smart antennasystem at the first base station 102 for receiving data from the userterminal, and the base station then also determines a processingstrategy for its antenna system to transmit an acknowledgment signal toits associated user terminal as a further reverse poll acknowledgementsignal.

While one embodiment of the invention is used in only one base stationhaving a smart antenna system, in accordance to other embodiments, thecommunication system 100 may have base stations that each includes sucha smart antenna system. In one embodiment, the first base station 102and one or more second base stations 111 use identically configured setsof sequential time intervals, so that the first set of sequential timeperiods and the further sets of sequential time intervals have identicalstructure.

The signals shown in FIG. 3B are for a TDMA system that includes TDD, souplink signals and downlink signals are grouped together to reduce thenumber of times the smart antenna system of the base station switchesfrom uplink to downlink. As an alternate to the signals shown in FIG.3B, the order of time periods may change, for example, when the basestation uses frequency domain duplexing (FDD), wherein the downlinkfrequency and the uplink frequency are different for communicating withthe same user terminal. One such alternative is shown in FIG. 3D. FIG.3E shows another alternative, which is similar to the arrangement ofFIG. 3B, but with shifted frame boundaries. Many other alternatives tothe arrangement of FIG. 3B are possible without departing from the scopeof the invention as set forth in the claims below.

Alternate Embodiments for Traffic Communication

One embodiment that utilizes the frame structure shown in FIG. 3 is ahalf duplex embodiment in which any uplink data transfer period of theset of frames is not necessarily associated with a downlink datatransfer period for the same user terminal.

In accordance with one alternate half-duplex embodiment, theacknowledgement transfer period in a frame of the sequence of frames foracknowledging uplink data transfer is included in a future—e.g., thenext—designated downlink data transfer period for the user terminal.Thus, data transferred on the downlink during a downlink data transferperiod may include acknowledgement data and/or may include trainingdata. Furthermore, there is a downlink data transfer period for everyuplink data transfer period.

Furthermore, in accordance with another alternate half-duplexembodiment, the acknowledgement transfer period in a frame foracknowledging downlink data transfer (or responding to an accessassignment message) is included in a future—e.g., the next—designateduplink data transfer period for the user terminal. Thus, datatransferred during an uplink data transfer period may include trainingand/or identification data and/or acknowledgement data. Furthermore,there is an uplink data transfer period for every downlink data transferperiod.

FIG. 4 is a set of transmission time diagrams illustrating transmissionsequences in the case of yet another alternate embodiment that utilizesa full duplex system and thus referred to herein as a full duplexalternate embodiment. FIG. 4A shows the overall division of time into asequence of contiguous frames of equal duration. Three completesequential frames are illustrated in FIG. 4A.

An exemplary data transfer segment for a particular channel is shown ingreater detail in FIG. 3B. The frame in accordance with the full duplexalternate embodiment of the invention is subdivided into a number ofuplink data transfer periods, U1, U2, U3, etc. and the same number ofdownlink data transfer periods D1, D2, D3, etc. In the exampleillustrated in FIG. 4B there are five downlink and uplink data transferperiods, corresponding to accommodation of at least five active userterminals. Each active user terminal is assigned to an uplink and adownlink data transfer period, as described herein using an accessassignment message from its associated base station. Other embodimentsmay have more or fewer downlink and uplink data transfer periods in eachframe. For example, one embodiment uses a frame structure with threeuplink and three downlink data transfer periods in each frame.

In accordance with the full duplex alternate embodiment, theacknowledgement transfer period in a frame of the sequence of timeintervals for acknowledging uplink data transfer is included in afuture—preferably the next—designated downlink data transfer period forthe user terminal. Furthermore, the acknowledgement transfer period in aframe of the sequence of time intervals for acknowledging downlink datatransfer (or responding to an access assignment message) is included ina future—preferably the next—designated uplink data transfer period forthe user terminal.

Initiating data communication from a base station is carried out asdescribed above for one half-duplex embodiment described herein. Thebase station first sends a paging message. The user terminal respondswith a random access request. The base station responds with an accessassignment message that includes specifying the uplink and downlink timeperiods to use for traffic communication.

When the user terminal receives the access assignment message, it sendsan acknowledgement signal during its assigned uplink traffic channel.The signal may include training data and/or identification data for useby its associated base station in determining an advantageous smartantenna processing strategy for the radio link between the user terminaland the base station. The set of sequential time periods for first basestation 102 is coordinated with the sets of sequential time periods forbase station of other base stations, such as second base station 111, sothat the responses to access assignment messages from user terminals areat time/frequency locations known a base station, so that a basestation, for example first base station 102, receives not onlysignals—including interfering signals—from its associated userterminals, but also from co-channel user terminals associated with otherbase stations such as second base station 111. The advantageous smartantenna processing strategy for communicating with the user terminal isdetermined to include interference mitigation from the co-channelinterferers (on the uplink) and towards the co-channel interferers (onthe downlink).

Furthermore, when the base station receives uplink traffic data from atleast one of its associated user terminals, it transmits anacknowledgement signal to such a user terminal in the downlink datatransfer period corresponding to the uplink data transfer period inwhich it received the uplink data.

Thus, a signal is sent by a user terminal in response not only to anaccess assignment message from its associated base station, but also asan acknowledgment to downlink traffic data received from its associatedbase station.

Furthermore, in accordance with this full duplex alternate embodiment,uplink traffic data also includes training data and identification data,and the base station uses such data to determine a processing strategyfor its smart antenna system.

Thus, data transferred on the downlink during a downlink data transferperiod may include training data and may include acknowledgement data,such as ACK and/or NACK data, or other mechanism for acknowledgement,and data transferred during an uplink data transfer period may includetraining an/or identification data and/or acknowledgement data, such asACK and/or NACK data, or some other acknowledgement data. When atransmitting entity receives a NACK or does not receive an expected ACK,or otherwise knows there has been unsuccessful reception, itre-schedules transmission of the data.

Yet another alternate embodiment of the invention is now described. Inaccordance with this alternate embodiment, for initiating communicationfrom the base station, the base stations 102 and 111 each transmits adownlink polling signal to its respective associated active userterminals prior to receiving a data transmission from such userterminals. This polling is done in order to facilitate determination ofa smart antenna processing strategy for particular packet datacommunication, in accordance with an embodiment of the presentinvention. In one embodiment, the downlink polling is carried out by thefirst base station 102 and the one or more second base stations 111within a provided first set of sequential time intervals for first basestation 102 and within provided further sets of sequential timeintervals for each of second base stations 111, with each of the timeintervals including a data transfer segment that has a selected numberof downlink transfer periods, including forward polling periods, and anumber of associated uplink transfer periods, each associated with aforward polling period, and a number of traffic data transfer periods.

FIG. 5 is a set of transmission time diagrams illustrating thetransmission sequences in the case of this alternate embodiment. FIG. 5Ashows the overall division of time into a sequence of contiguous framesof equal duration. Each frame includes a signalling segment, fortransmission and reception of system overhead signals, such as cellularoverhead, and a data transfer segment. Three complete sequential framesare illustrated in FIG. 5A. For purposes of system timing control, eachsignalling segment starts with a frame marker signal from the basestation to synchronize all remote units to the timing sequence of thebase station.

One aspect of the present invention relates primarily to thearrangements of signals within the data transfer segment of each frame,and accordingly an exemplary data transfer segment for a particularchannel is shown in greater detail in FIG. 5B.

The data transfer segment in accordance with this alternate embodimentof the invention is subdivided into a number of forward polling periodsF1, F2, F3, etc. a number of reverse polling periods R1, R2, R3, etc.,and a number of traffic data transfer periods D1, D2, D3, etc. In theexample illustrated in FIG. 5B there are five forward polling periods,five reverse polling periods and five traffic data transfer periods,corresponding to accommodation of at least five active user terminals.Each active user terminal is assigned to a signal channel and a forwardpolling period and a reverse polling period.

First base station 102 and the other base stations 111 transmit theirdownlink polling signals in their respective forward polling periods.Each user terminal that receives a polling signal from its associatedbase station responds to the polling signal at an uplink transfer periodassociated with the forward polling period. The associated uplinktransfer period is part of the traffic data transfer period of the setof sequential time intervals of its associated base station. The firstand further sets of sequential time intervals are such that the responseof the user terminals to the downlink polling occurs at associateduplink transfer periods and frequency/code channels known to first basestation 102.

Base station 102 receives the responses and uses the responses todetermine a downlink processing strategy for the smart antenna system,and transmits data signals to its active associated user terminals usingthe determined downlink processing strategy. In one TDMA embodiment, thetimings of base stations are synchronized, and the responses of thedesired user terminals 105, 106, 107, 108, and the interfering userterminals 109, 110 to the downlink polling from such user terminals'respective base stations occur at the same timeslot and in the samefrequency channel. The determined smart antenna processing strategyincludes interference mitigation towards such interfering co-channelremote terminals.

For initiating communication from one of the user terminals associatedwith the first base station 102, when the user terminal desires to senda data transmission to the first base station 102, the user terminaltransmits a reverse polling signal during a reverse polling period whichis received by the first base station 102. The first base station 102now transmits a reverse poll acknowledgement signal to the userterminal, including transmitting information to the user terminal toindicate to the user terminal that the reverse poll has been receivedand including data to designate the traffic data transfer period andfrequency channel for receiving a data transfer on the uplink from theuser terminal.

The user terminal then sends a data transfer signal, during thedesignated uplink traffic data transfer period. The data transfer signalmay include training data in a training data segment of the uplinktraffic data transfer period, as shown in FIG. 5D. The base stationreceives the signal from the user terminal. Other base stations such assecond base station 111 may also be receiving signals in response toreverse polling acknowledgement from their respective bases stations,and these signals may interfere with the data transfer signal to firstbase station 102. In accordance with one embodiment of the invention,the first and further sets of sequential time intervals are such thatthe data transfer signals are sent in response to the reverse pollacknowledgement signals at uplink traffic data transfer periods andfrequency/code channels known to first base station 102. First basestation 102 receives the responses to the reverse pollingacknowledgements and uses the responses to determine a processingstrategy for the smart antenna system for receiving from its activeassociated user terminals.

First base station 102 then receives data signals from its activeassociated user terminals using the determined smart antenna processingstrategy. In one TDMA embodiment, the timings of base stations aresynchronized, and the responses of the desired user terminals 105, 106,107, 108, and possibly interfering user terminals 109, 110 to thereverse poll acknowledgements from such user terminals' respective basestations may occur at the same timeslot and in the same frequencychannel. The smart antenna processing strategy is determined to includeinterference mitigation from such interfering users.

In one embodiment, the system 100 includes the first base station 102and one or more other base stations 111 that each have a smart antennasystem, and the first base station 102 and other base stations 111 useidentically configured sets of sequential time intervals, so that thefirst set of sequential time periods and the further sets of sequentialtime intervals have identical structure. In another embodiment, only thefirst base station 102 has a smart antenna system.

As an alternate to the signals shown in FIG. 5B, it might beadvantageous to provide the reverse polling period first and the forwardpolling period second as shown in FIG. 5C. In this event, the basestation can acknowledge the receipt of the reverse polling signal from auser terminal and designate a data transfer segment by a selectedreverse poll acknowledgment signal during the corresponding forwardpolling period. In the case of forward polling, as described above, anacknowledgment is not required, since the transmission of the trainingsignal by the user terminal at the start of the data transfer periodconstitutes sufficient knowledge to the base station that the userterminal has received the forward polling signal.

Alternate embodiments may use different ways of increasing thelikelihood of successful reception at remote terminals of the overheadsignalling and polling signals transmitted by the base stations. In onealternative, the overhead signalling and polling signals are transmittedover a broad beam using the elements of array 104 (see for example, U.S.patent application Ser. No. 08/988,519 to Goldburg, filed Dec. 12, 1997and assigned to the assignee of the present invention).

Alternate embodiments may further use a pilot tone rather than atraining signal in the responses of the user terminals. Other alternateembodiments may not include a training signal or pilot tone, and in sucha case, known “blind” methods may be used to determine the weightingparameters for the smart antenna system of the first base station 102.

In yet other alternate embodiments, modifications may be made to otherknown polling arrangements that allow to obtain weighting parameters fora smart antenna system of a base station. One such protocol that may bemodified it that proposed by Z. Zhang and A. S. Amapora in “Performanceof a modified polling strategy for broadband wireless LANs in a harshfading environment,” Proc. GLOBECOM' 91, (“Zhang”), A. S. Amapora and S.V. Krishnamurthy, “New adaptive MAC layer protocol for wireless ATMnetworks in harsh fading and interference environments,” Proc. ICUPC'97, San Diego, Calif., 1997 (“Amapora and Krishnamurthy”), and S. V.Krishnamurthy, A. S. Amapora, and M. Zorzi, “Polling based media accessprotocol for use with smart adaptive array antennas,” Proc. ICUPC' 98,pp. 337-341, 1998 (“Krishnamurthy”). Zhang proposes a token-basedprotocol that allows a base station's smart antenna system toperiodically update its weighting parameters by sequentially pollingeach remote terminal. A remote terminal responds to a polling requesteither with an information request or an unmodulated pilot tone, andeither response may be used to update weights. To modify the Zhangmethod to incorporate the invention, the protocol used by the basestation and one or more other base stations are coordinated so that theinformation request or the unmodulated pilot signal received from remoteuser terminals of other base stations such as second base station 111occur at time/frequency locations known to first base station 102, andare used to determine a processing strategy for the smart antenna systemof first base station 102 to provide interference mitigation for or fromuser terminals associated with the other base stations. Amapora andKrishnamurthy propose a media access (MAC) protocol that claims toallows for faster adaptation than Zhang. Each transmission, in eitherdirection, is immediately preceded by a remote to base-station pilotsignal used to immediately adapt the array to that remote. Modificationof the Amapora and Krishnamurthy method would be similar. In theKrishnamurthy scheme, any remote may piggyback its information requeststo any information transfer between the base station and itself.Therefore, only remotes that have not transferred information in theprevious frame are polled in the present frame. The frame size thereforenot fixed but varies at least according to the number of polls included.In one variant, the base station uses limited polling in that at eachpoll, a remote sends one outstanding request to the base station, and inthe second variant, the base station exhaustively polls each remote, anda remote, when polled sends all of its outstanding requests. A modifiedKrishnamurthy scheme may also be accommodated in an alternate embodimentof the present invention, in which the protocol used by a particularbase station is coordinated with the protocols used by other basestations so that responses by remote terminals occur at time/frequencylocations available to the particular base station.

While much of the above discussion has been for a TDMA system, theinvention may also be implemented in a FDMA and a CDMA system.

The invention may be employed in hardware, software, or a combinationthereof. For example, in one embodiment, the invention is implemented atleast in part by information stored on a machine-readable medium, whichinformation represents a set of instructions that, when executed by amachine (e.g., a data processing system employed by a communicationdevice such as a base station or user terminal), cause the machine toperform at least a portion of a method embodied by the invention. Themedium may include a storage material (e.g., magnetic storage disk,optical disk, etc.) and/or a memory device (e.g., ROM, RAM, DRAM, SRAM,etc.). One or more general-purpose and/or dedicated processors, such asdigital signal processors (DSPs) may be employed by a base station oruser terminal operating in conjunction with an embodiment of the presentinvention.

A user terminal in the context of the invention may represent varioustypes of communication devices, and may be coupled to input and/oroutput devices and/or processing devices to provide various types offunctionality, such as voice communications, data communications overthe Internet or other data communication network.

It should further be appreciated that although the invention has beendescribed in the context of communications and in particular, cellularcommunications systems employing at least one base station having asmart antenna system, the invention is not limited to such contexts andmay be utilized in various wireless applications and systems, forexample in a system that includes a communication device such as acommunication station that includes a smart antenna system. Furthermore,the invention is not limited to any one type of architecture or airinterface, and thus, may be utilized in conjunction with one or acombination of TDMA, FDMA, or CDMA, and TDD or FDD, or otherarchitectures/protocols.

Thus, while there has been described what is believed to be thepreferred embodiments of the invention, those skilled in the art willrecognize that other and further modifications may be made theretowithout departing from the spirit of the invention, and it is intendedto claim all such changes and modifications as fall within the scope ofthe invention.

1. A method for receiving a paging signal in a data frame from a basestation, the frame defined by a communication protocol as having a groupof sequential time slots being data transfer periods within the frame,comprising: receiving a paging signal at a mobile user terminal in asub-period of a data transfer period of a data frame as defined by thecommunication protocol; receiving a repetition of the paging signal in adifferent sub-period of the data frame to provide different spatialsignatures between the paging signal and the repetition of the pagingsignal, wherein the repetition is one of one or more repetitions, wherethe number of repetitions is based on estimation of proximity of themobile user terminal to the base station, the estimation based on datasent from the mobile user terminal to the base station in a negotiationsequence; and processing the paging signal and the repetition of thepaging signal to obtain paging data.
 2. The method of claim 1, whereinreceiving the paging signal in the sub-period of the data transferperiod comprises: receiving the paging signal in a sub-timeslot of adownlink timeslot.
 3. The method of claim 2, wherein receiving thepaging signal in the sub-timeslot comprises: receiving the paging signalin a half-slot of the downlink timeslot.
 4. The method of claim 1,wherein receiving the paging signal in the sub-period of the datatransfer period comprises: receiving the paging signal in asub-frequency-band of a downlink frequency band.
 5. The method of claim4, wherein receiving the paging signal in the sub-frequency-bandcomprises: receiving the paging signal in a frequency band one half thebandwidth of the data transfer frequency band.
 6. The method of claim 1,wherein receiving the repetition of the paging signal comprises:receiving the repetition of the paging signal in a sub-period of adifferent data transfer period of the data frame.
 7. The method of claim1, wherein receiving the repetition of the paging signal comprises:receiving a signal having adjusted signal transmission characteristicsto account for changes in an interference environment associated withthe paging signal.
 8. An article of manufacture comprising amachine-accessible storage medium having information representinginstructions, which when executed, cause a mobile user terminaltransceiver system including a processor to perform operations includingthe user terminal to: receive a paging signal in a sub-period of a datatransfer period of a data frame as defined by the communicationprotocol, the data frame defined by a communication protocol as having agroup of sequential slots; receive a repetition of the paging signal ina different sub-period of the data frame to provide different spatialsignatures between the paging signal and the repetition of the pagingsignal, wherein the repetition is one of one or more repetitions, wherethe number of repetitions is based on estimation of proximity of themobile user terminal to the base station, the estimation based on datasent from the mobile user terminal to the base station in a negotiationsequence; and process the paging signal and the repetition of the pagingsignal to obtain paging data.
 9. The article of manufacture of claim 8,wherein the instructions to cause the user terminal to receive thepaging signal in the sub-period of the data transfer period comprisesinstructions to cause the user terminal to: receive the paging signal ina sub-timeslot of a downlink timeslot.
 10. The article of manufacture ofclaim 9, wherein the instructions to cause the user terminal to receivethe paging signal in the sub-timeslot comprises instructions to causethe user terminal to: receive the paging signal in a half-slot of thedownlink timeslot.
 11. The article of manufacture of claim 8, whereinthe instructions to cause the user terminal to receive the paging signalin the sub-period of the data transfer period comprises instructions tocause the user terminal to: receive the paging signal in asub-frequency-band of a downlink frequency band.
 12. The article ofmanufacture of claim 11, wherein the instructions to cause the userterminal to receive the paging signal in the sub-frequency-bandcomprises instructions to cause the user terminal to: receive the pagingsignal in a frequency band one half the bandwidth of the data transferfrequency band.
 13. The article of manufacture of claim 8, wherein theinstructions to cause the user terminal to receive the repetition of thepaging signal comprises instructions to cause the user terminal to:receive the repetition of the paging signal in a sub-period of adifferent data transfer period of the data frame.
 14. The article ofmanufacture of claim 8, wherein the instructions to cause the userterminal to receive the repetition of the paging signal comprisesinstructions to cause the user terminal to: receive a signal havingadjusted signal transmission characteristics to account for changes inan interference environment associated with the paging signal.
 15. Auser terminal in a wireless communication system that receives a pagingsignal in a data frame from a base station, the frame defined by acommunication protocol as having a group of sequential slots, the userterminal comprising: a transceiver system to receive a paging signal ata mobile user terminal in a sub-period of a data transfer period of adata frame as defined by the communication protocol, and receive arepetition of the paging signal in a different sub-period of the dataframe to provide different spatial signatures between the paging signaland the repetition of the paging signal, wherein the number ofrepetitions is limited and selected based on estimation of proximity ofthe user terminal to the base station, the estimation based on data sentfrom the mobile user terminal to the base station in a negotiationsequence; and a processing system in communication with the transceiversystem to process the paging signal and the repetition of the pagingsignal to obtain paging data.
 16. The user terminal of claim 15, whereinthe transceiver system is to receive the paging signal in a sub-timeslotof a downlink times lot.
 17. The user terminal of claim 16, wherein thetransceiver system is to receive the paging signal in a half-slot of thedownlink timeslot.
 18. The user terminal of claim 15, wherein thetransceiver system is to receive the paging signal in asub-frequency-band of a downlink frequency band.
 19. The user terminalof claim 18, wherein the transceiver system is to receive the pagingsignal in a frequency band one half the bandwidth of the data transferfrequency band.
 20. The user terminal of claim 15, wherein thetransceiver system is to receive the repetition of the paging signal ina sub-period of a different data transfer period of the data frame. 21.The user terminal of claim 15, wherein the transceiver system is toreceive a signal having adjusted signal transmission characteristics toaccount for changes in an interference environment associated with thepaging signal.